This invention relates to isomerization of 2-branched-1-olefins, present in minor amounts in mixture with vinyl olefins, using a zeolitic catalyst.
In certain reactions it is desirable to use relatively pure straight chain vinyl olefins. For example, in the formation of straight chain alcohols, it is desirable to start with straight chain vinyl olefins. The straight chain vinyl olefins may be reacted with trialkyl aluminum to form new trialkyl aluminum compounds having alkyl groups corresponding to the vinyl olefins; then the new trialkyl aluminum compounds are oxidized to aluminum alkoxides; and finally the alkoxides are hydrolyzed to form straight chain alcohols.
However, if vinylidene olefins (2-branched-1-olefins) are present in the straight chain vinyl olefin feed, non-linear chain alcohols will be formed, which is generally undesirable.
Vinylidene olefins have the structure: ##STR1## where n is zero or an integer, and R is an alkyl group.
It is desirable to convert the vinylidene olefins to tri-substituted ethylene compounds because the tri-substituted ethylene compounds interfere less with reactions, such as reactions leading to formation of linear alcohols, then do the vinylidene olefins.
Tri-substituted ethylene compounds have the formula: ##STR2## where R, R.sup.1 and R.sup.2 are the same or different alkyl groups.
An object of the present invention is to reduce the amount of vinylidene olefins present in a mixture containing vinyl olefins and vinylidene olefins. It is also an object of the present invention to carry out such reduction while retaining most of the vinyl olefins intact. Such reduction of vinylidene olefins is carried out using a particular isomerization process as described below.
The isomerization of olefins is known in the art. For example, Rabo, in Zeolite Chemistry and Catalysis, ACS Monogram No. 171, 1976 at page 335, discloses the isomerization of 1-butene to 2-butene using a Y zeolite catalyst. However, it is important to note that this type of isomerization would be undesirable in the present invention, at least to the extent that it reduces the amount of straight chain vinyl olefin.
U.S. Pat. No. 3,686,250 (Lanier) discloses a process for producing hydrocarbon aluminum compounds by reacting vinyl olefins with trialkyl aluminum. The Lanier patent also discloses that the vinyl olefin feedstock may be treated to reduce the content of vinylidene olefins. The treatment disclosed is selective isomerization wherein the vinylidene olefins are converted to tri-substituted olefins without significantly altering the amount of co-present vinyl olefins. Catalyst disclosed for the isomerization reaction in the Lanier patent are:
"silica gel, silicated alumina, crystalline alumino silicates (molecular sieves), activated alumina, ion exchange resins, acid clays such as montomorillonite, attapulgite, mordenite, diatomaceous earth, and so forth." PA0 "Of all the foregoing, the highly acidic materials generally have high initial reactivity; however, they are deactivated at an undesirably high rate by traces of impurities so that those materials of moderate acidity such as silica gel, activated alumina, and acidic clays are generally preferred both from a long term activity point of view and from a low cost viewpoint."
According to the Lanier patent: